Refining mineral lubricating oils



Patented Sept. 6, 1938 2,128,958 REFINING MINERAL LUnnIca'rmG oILs Martin Mueller-Cunradi and Robert Ulotli, Ludwigshafen-on-the-Rhin e, Germany, assignors to I. G.- Farbenindustrie Aktiengeseilschait, Frankiort-on-the-Main, Germany No Drawing.

Application April 26, 1934, Serial No. 722,503. In Germany May 5, 1933 1 Claim.

The present invention relates to improvements in the production of lubricating oils, more particularly by extraction by means of selective solvents.

5 We have found that the temperature-viscosity curve of mineral lubricating oils is quite considerably improved by subjecting the said oils to extraction by means of certain solvent mixtures one essential constituent of which is acetonitrile, methanol or formamide. The other essential constituent of the solvent mixtures used according to the present invention may be a benzene derivative or heterocyclic compound containing nitrogen'and/or oxygen, such as phenol, ortho-cresol, meta-cresol, para-cresol, raw cresylic acid, nitrobenzene, nitrotoluene, aniline, chloraniline, nitraniline, toluidine, xylidine, methylaniline, nitrophenols, benzaldehyde,

benzonitrile, furfurol, furfuryl alcohol or pyridine; or it may be an aliphaticcompound containing nitrogen and/or chlorine, such as ethylene diamine, ethylene dichloride, propylene dichloride, ethylene chlorhydrine, di-chloro-ethyl ether or ethyl chloracetate; or it may be an allphatic compound containing at least two oxygen atoms, such as the mono-methyl ether of ethyl ene glycol, the acetate of ethylene glycol monoethyl ether, glycol diacetate, methyl formate or vinyl esters; or it may be an aliphatic alcohol,

such as the butyl or amyl alcohols or cyclohexanol, or an aliphatic ketone such as acetone,

- or an aliphatic aldehyde such as croton aldehyde, or an unsaturated aliphatic ether such as the vinyl ethers of low molecular alcohols.

We prefer to use solvent mixtures which contain derivatives of benzene containing nitrogen and/or oxygen, such as phenol, nitrobenzene, aniline or benzonitrile.

Of course, the mixtures used should be selected so that they are only soluble in the mineral oils to a limited extent. For example, when working with the preferred solvent mixtures, the treated oil will contain only up to between 10 and 20 per cent, by volume, of the solvents.

The proportions, in which the single constituents are present in the solvent mixture, may vary within very wide limits. For example, the amount of acetonitrile, methanol or formamide may vary between 5 and 95 per cent, by volume,

of the mixture. We prefer to use an amount between 30 and '70 per cent of the mixture. When using mixtures of methanol with phenol, care should be taken that the mixture does not contain substantially more than 50 per cent of 5 phenol.

.Working at about room temperature is usually most convenient. If desired, the process may be carried out under increased pressures of any desired height, By the simultaneous employ- 10 ment of the said mixtures of solvents, results are obtained which are unobtainable by the employment of the said substances'alone or even by the employment of the components of the mixture consecutively. A special advantage of 15 the process according to this invention is that comparatively small amounts of solvent are em! ployed and that in a single operation lubricating oils having a very flat temperature-viscosity curve can be obtained in very high yields. The 20 process may be usefully employed not only with paraflin base lubricating oils, but also with naphthenic and aromatic lubricating oils from which otherwise oils having a flat temperatureviscosity curve can only be prepared with dif- 25 ficulty.

-The process may be carried out for example by causing the said solvents separately or in, admixture to flow into the oil to be improved in a stirring vessel and by stirring the whole 30 vigorously. When the whole has been thoroughly intermixed, the mixture is allowed to separate. The layers are separated from each other while warm or cold and the oil in each layer is freed from, solvent by one of the usual 35 methods, as for example by distillation.

The process may also be carried out by leading the oil in a column continuously in countercurrent to the said solvents, the mixtures which are obtained being allowed to settle and the 40 layers formed then being further worked up. Devices, such as mixing nozzles and turbo mixers, may also be employed.

If desired the settling may be accelerated by centrifuging.

After settling two layers are obtained, one of which (usually the upper layer) consists mainly of oil and contains only small amounts of the solvents, while the other layer consists of a solution of the. resins and other undesirable mat- 50 ter. The oils obtained from the first-mentioned layer arepaler than the initial oils, their tar value is lower and their stability to light better. They are distinguished by a high viscosity index which depends in each case on the quality of the initial oils. Thus from an oil having a viscosity index of 80, an oil having a viscosity index of 115 or more may be obtained in a high yield. If necessary, in order to increase the viscosity, substances having this effect may be added, as for example polymerization products of isobutylene, or other oils, obtained for example in the said manner from cylinder oils may-be admixed therewith.

The setting point of the improved oils is generally speaking higher than that of the initial oils. If the initial oils contain paraffin wax, the

latter separates in a readily removable form in the layer containing the oil. The paraffin wax may be removed in order to improve the setting point; agents lowering the setting point may, however, also be added. Agents preventing ageing, agents preventing resinification, deblooming agents, dyestuffs and agents producing fluorescence may also be incorporated.

The extracts obtained from the other layer are, depending on the character of the initialoils and the mixtures employed, from dark brown oils to resinous greases which often have a strongiy negative viscosity index. Their setting point is generally speaking lower than that of the initial oils. These extracts are suitable as agents lowering the setting point, if desired after fresh treatment with the solvent mixtures according to the present invention.

The following examples will further illustrate the nature of this invention but the invention is not restricted to these examples. The parts are by volume.

Example 1 50 parts of nitrobenzene and 50 parts of acetonitrile are added at 50 C. to 100 parts of a lubricating oil of red transparency and greenish blue fluorescence having a specific gravity of 0.910, a setting point of 95 below zero C., a viscosity of 13.1 Engler at 38 C. and 1.8 Engler at 100 C. and a viscosity index of the mixture is stirred for 15 minutes in a stirring vessel and then allowed to stand. After settling, an upper oil layer is obtained which contains about 20 per cent of the solvent employed. After distilling off the latter parts of a paler oil are obtained having a specific gravity of 0.899 at 18 C., a viscosity of 12.1 Engler at 38 C. and 1.8 Engler at C. and a viscosity index of 92. The extract contained in the lower layer is black-brown, has a specific gravity of 1.005 at 17.5 C., a viscosity of 72.7 Engler at 38 C. and 2.48 Engler at 100 C. and a viscosity index. of about -80.

If the same initial oil be treated in an identical manner with 50 parts of nitrobenzene, 80 parts of oil having a viscosity index of 90 (viscosity 12.2 Engler at 38 C. and 1.8 Engler at 100 C.) and 20 parts of dark brown extract having a viscosity index of 68 (viscosity 18.3 Engler at 38 C. and 1.95 Engler at 100 C.) are obtained. The upper oil layer contains about 60 per cent of the nitrobenzene.

The resulting oil having a viscosity index ,of 90 is treated with 50 parts of acetonitrile; 79 per cent by weight of an oil having a viscosity index of 92 are obtained.

When the same initial oil is treated with 100 parts of .acetunitrile there are obtained from the lower layer 98 parts of an oil the viscosity of which is scarcely altered; when treated with 1000 parts of acetonitrile, 88 parts of an oil having a viscosity index of 90 are obtained. Even by treatment with still larger amounts of acetonitrile, the viscosity index is not appreciably increased. From the other layer, 1.6 parts of a product having a viscosity index of are obtained.

The oil which has been treated with 100 parts of acetonitrile is dissolved at 50 C. in 50 parts of nitrobenzene and stirred while cooling to 18 C. From the upper oily layer there are obtained 83 parts of oil having a viscosity index of 90 and from the lower layer 14.5 parts of oil having a viscosity index of '70.

Example 2 100 parts of the initial oil employed in Example 1, are mixed at 20 C. with a mixture of 50 parts of nitrobenzene and 50 parts of methanol and treated as described in Example 1. 83 parts of oil having a viscosity index of 100 are obtained from the upper layer. By treating the same 011 with 100 parts of methanol alone, there is no increase in the viscosity index.

Example 3 100 parts of the initial oil employed in Example 1 are treated at 20 C. with 100 parts of phenol and 100 parts of methanol. 85 parts of oil having a viscosity index of 99 and a setting point of 5 below zero C are obtained from the upper layer. The extract has a viscosity index of 40 (viscosity 49.0 Engler at 38 C. and 2.25 Engler at 100 C.). 15 per cent of the amount of solvent employed are contained in the oil.

By treating the same oil with 100 parts of phenol alone, 78.5 parts of an oil having a viscosity index of 88 are obtained from the upper layer and 21.2 parts of extract having a viscosity index of 55 from the lower layer. The oil contains about 35 per cent of the solvent employed.

Example 4 100 parts of phenol and 36 parts of acetonitrile are added at 50 C. to 100 parts of the initial oil employed in Example 1 and the whole is stirred until it has cooled to 20 C. After working up, 87.5 parts of oil having a viscosity index of 94 are obtained from the up'perlayer. The extract has a viscosity index of about 100.

*Ezample 5 60 parts of benzonitrile and 60 parts of acetonitrile are added at 20 C. to 100-parts of the initial oil employed in Example 1, the whole being treated in the manner described in the said example. 86 parts of an oil having a viscosity index of 92 are obtained from the upper layer and 13.4 parts of oil having a viscosity index of 40 from the lower layer. By carrying out the same treatment of the same oil with 60 parts of benzonitrile alone, 68 parts of oil having a viscosity index of 89 and 31.5 parts of oil having a viscosity index of 63 are obtained.

Example 6 100 parts of the same initial oil as treated according to Example 1 are treated three times at 20 C. each with a mixture of 42 parts of nitrobenzene and 33 parts of acetonitrile in such a manner that the spent solution is withdrawn and the supernatant mixture of the solvents and oil is treated with fresh solvent mixture. In this way 76 parts of oil having a viscosity index of 111 and a pour point of 2.5 below zero C. and 23.3 parts of an extract having a viscosity of 0 and a pour point of 17 below zero C. are obtained. The refined oil is mixed with 0.5 per cent of a pour point depressant prepared according to British specification No. 349,071 and 1.5 per cent of a polymerization product of isobutylene whereby an excellent motor oil having a pour point of 32' below zero C. and a viscosity index of 120 is obtained. The viscosities of this oil are 20.3 Engler at 38C. and 2.53,Engler at 100 C.

When treating the same initial oil with 125 parts of nitrobenzene without acetonitrile, 46 parts of refined oil having a viscosity index of 106 and 53 parts of an extract having a viscosity index of-57 are obtained.

Example 7 index of 80 and 18.8 parts of an extract having a viscosity index of 50.

When treating the initial oilwith 100 parts of nitrobenzene alone there are obtained 53.3 parts of an oil having a viscosity index of 72 and 46.1 parts of an extract having a viscosity index of 24.

Example 8 A synthetic lubricating oil obtained by the condensation of gaseous oleilnes with a middle oil and having a viscosity at 38 C. of 14.8 Engler and at 100 C. of 1.76 Engler, a viscosity index of 45, a specific gravity at 20 C. of 0.948, a refraction index no" of 1.5350 and a pour point of 10 C. is treated at 20 C. with 100 parts of nitrobenzene and 75 parts of acetonitrile. There are obtained 65.5 parts of an oil having a viscosity index of 80' and a pour point of 15 C. and 38.6 parts of an extract having a viscosity index of -60 and a pour point of 0 C.

when treating the said initial oil with nitrobenzene alone only very small amounts of an jecting a mineral lubricating oil to extraction by.

means of a mixture consisting essentially of nitrobenzene and acetonitrile.

MARTIN MUELLER-CUNRADI. ROBERT ULOTH. 

